Smelting plant and method

ABSTRACT

Iron-containing materials are loaded into the top of a shaft furnace to form therein an upright column of the materials. A burner forms a flame above the floor of the furnace to heat the base of the column and thereby melt the materials at the base of the column into a liquefied-iron melt on the floor of the furnace and a layer of slag on the melt. In addition this flame formed by the burner forms a deposit in the furnace on which the column is supported. Slag is continuously withdrawn from the furnace at a location substantially level with the deposit and the melt is withdrawn from the furnace at a location below the layer of slag and is heated as it is withdrawn. This melt is withdrawn through an iron-drain conduit having an outlet end vertically positioned to be horizontally even with the lower surface of the slag and a refining vessel working inductively or by means of an electric arc may be provided in this outlet conduit for the continuous transformation of the liquefied iron into steel.

BACKGROUND OF THE INVENTION

The present invention relates to a method of and an apparatus forsmelting. More particularly this invention concerns a system and plantfor smelting and refining iron in a shaft furnace.

It is possible in a shaft furnace to smelt iron-containing scrap, spongeiron, pelletized iron-containing ore, iron dross, and the like byintroducing this iron-containing material into the top of the furnace toform therein an upright column of such material. A burner heats the baseof the column to form at the bottom of the shaft furnace aliquified-iron melt covered by a layer of slag. In addition this burnercauses the formation of a scale or deposit on the refractory lining ofthe furnace and the column is supported on this deposit as described inmy copending and commonly owned patent application Ser. No. 651,526filed Jan. 22, 1976.

The burner at the bottom of the furnace typically mixes right in thefurnace oxygen and combustible. This hot flame and the extremely activeFeO slag tend to eat away the refractory furnace lining at the floor andlower regions of the walls of the furnace. It is essential to minimizethis erosion in the furnace as well as in any other treatment vessels.Also the liquified iron in the melt at the bottom of the furnace mustnot be allowed to solidify.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved method of and apparatus for smelting which advances principlesset forth in my above-cited application Ser. No. 651,526.

Yet another object is the provision of an improved smelting method andplant which minimizes the damage that can be done by the very hot andcorrosive Fe0 slag to the furnace lining without solidification of thismelt.

These objects are attained according to the present invention in a shaftfurnace wherein slag is continuously withdrawn from the furnace at alocation substantially level with the deposit formed by the flame abovethe floor of the furnace and the melt is withdrawn from the furnace at alocation which determines the vertical position of the undersurface ofthe layer of slag and the melt is heated as it is withdrawn. Inaccordance with this invention the shaft furnace is provided with aniron-drain conduit having an inlet end opening into the furnace belowthe slag layer and an outlet end substantially at level of theundersurface of the slag layer so that the iron passes out of thefurnace through the conduit and remains at a level in the furnacedetermined by the level of the outlet end. This conduit may have anintermediate portion higher than both of its ends so as to function likea siphon. In effect the drain passage acts as a trap, permitting theliquified iron to flow out, but preventing reverse entry of air or anyother fluid back into the furnace.

Thus in accordance with the present invention the highly activeferrous-oxide slag is continuously removed from the shaft oven as itforms. Later stages in the plant are therefore not subjected to thishighly active material and even a possible reaction between this slagand the lining of the furnace is minimized since the slag layer ismaintained at the level of the continuously renewed iron-scale depositin the furnace. Since the liquid iron tends to flow down over this scaleto the bottom of the furnace the slag practically does not come intocontact with the lining of the furnace so that the service life of thislining is increased considerably. Furthermore the oxidizing regioninside the smelting zone is completely separated from any subsequentreducing stage.

According to yet another feature of this invention the melt isindirectly heated as it is withdrawn. It is possible to effect this bymeans of an induction coil according to the present invention or bymeans of refining electrodes in a refining vessel provided between theends of the iron-drain conduit. In the latter case in accordance withthis invention the slag drain is provided with a lateral branch thatfeeds a minor portion of the slag into this refining vessel so that theiron can be continuously refined into steel directly as it is withdrawnfrom the blast furnace.

When particularly pure materials are loaded into the blast furnace inaccordance with this invention it is possible merely to heat theiron-drain conduit in order to prevent solidification of the melt in itor in the bottom of the furnace. This also serves to make the melt morefluent and to protect the floor of the furnace from the heat of theflame and chemical activity of the slag. In such an arrangement theautomatic separation-out of the slag directly in the furnaces gives avery pure and a readily usable product.

It is therefore possible according to the present invention to processrelatively impure iron ores in a furnace without rapidly wearing out thelining of this furnace. The lining is, indeed, continuously protectedboth by the liquid-metal melt at the bottom of the furnace and by thedeposit formed naturally in the furnace by the burner. Virtually anymetal-containing material can be loaded into the top of such a furnaceand relatively pure metal can be withdrawn from the bottom. Inparticular the system can be used for the production of steel. Thecombination of this system with the subsequent refining step makes itpossible continuously to produce steel from the most disparate products.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section through a plant according to the presentinvention;

FIG. 2 is a section taken along line II--II of FIG. 1; and

FIGS. 3, 4 and 5 are vertical sectional views similar to FIG. 1illustrating further arrangements in accordance with the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1 a shaft furnace 1 is provided at its upper end with abell 3 that allows iron-containing materials to be introduced into thisfurnace to form a column 4 therein. This furnace tapers slightlyupwardly and is made of or lined with refractory material.

Above the floor 5 of this furnace there is provided a plurality ofburner tubes 6 connected to a common manifold 7. Each such burner tubeis actually formed as two concentric tubes to the inner one of which isfed pure oxygen and to the outer one of which is fed a combustible gasor atomized fuel so that a flame 8 is produced in the lower region 9 ofthe furnace 1 directly above the floor 5. This flame 8 heats the base ofthe column 4 and causes an iron-scale deposit to form on the lining ofthe furnace 1. The column 4 is supported on this deposit 10 which alsoserves to protect the furnace lining from the flame 8. An outlet pipe 9aserves to draw exhaust gases out of the top of the furnace 1. Such anarrangement is described in my above-cited application Ser No. 651,526whose entire disclosure is herewith incorporated by reference.

It is possible to use an annular burner spaced inwardly from the wallsof the furnace or to use a central flame in the furnace 1 instead of theplurality of burners 6 which open radially into the furnace as shown inFIGS. 1 and 2. In all such cases deposits 10 in the form of annularbosses are formed inside the furnace 1, although they may also be formedon the floor 5 thereof.

The flame or flames 8 liquifies iron in the column 4 and causes it toflow down over the deposits 10 and form a liquified-iron melt 13 lyingon the base 5 of the furnace 1, and a layer 14 of ferrous-oxide slag ontop of this melt 13. The floor 5 is inclined downwardly toward a drainoutlet 11 that opens into the bottom of a refining vessel 2. This drain11 opens inside the furnace below the level of the slag 14. In additionthere is provided another drain 12 which opens above the drain 11 and atthe level of the slag 14. This drain 12 terminates at 17 in the vessel 2above the drain 11. In addition another drain 15 extends from the bottomof the vessel 2 up to a level horizontally even with the underside ofthe layer 14. The height of the outlet end of the drain 15 thereforedetermines the depth of the melt 13 in the vessel 2 and in the bottom ofthe furnace 1. The slag 14 always floats on top of this melt so that aslag layer will be formed both in the furnace 1 and in the vessel 2 ontop of the melt.

Electrodes 16 are provided in the vessel 2 and serve to refine the irontherein into steel which exits at 15 from the vessel 2. Furthermore itis noted as best shown in FIG. 2 that most of the slag is drawn off fromthe slag drain 12 via a branch 17' as all of the slag produced in thefurnace 1 is not needed in the refining vessel 2.

The arrangement of FIG. 3 is identical to that of FIG. 1, with commonreference numerals being used for identical structure. Here, however, avessel 2a is provided which has an induction coil 18 that servesinductively to heat the iron coming out of the drain 11 before it exitsvia the drain 15. In this arrangement also the iron-drain 11, 15 has itsoutlet and at a level L horizontally even with or slightly above theunderside of the slag layer 14 and serving to establish the depth of themelts 13 in the furnace 1 and in the vessel 2a.

The arrangement of FIG. 4 has an inductive heater 19 provided adjacentthe drain 11 and serving to superheat the iron and to prevent it fromsolidifying as it is drawn out of the furnace 1. Such an arrangement isparticularly usable when relatively pure starting products are loadedinto the furnace 1 to form the column 4 so that the melt drawn off at 11is usable as is.

In the arrangement of FIG. 5 and inductive coil 20 surrounds the drainoutlet conduit 11. This coil 20, like the heater 19 and coil 18 isconnected to a suitable source of electrical power and insures that theiron does not solidify before it exits from the drain 15.

With the arrangement described above it is possible continuously tosmelt iron, using a wise variety of starting products. The lining of thefurnace 1 is protected by the melt 13 and the deposit 10 so that theservice life of this furnace is greatly increased. Furthermore it ispossible to operate continuously since the slag is withdrawn at 12 abovethe level L.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofsystems differing from the types described above.

While the invention has been illustrated and described as embodied iniron-smelting systems, it is not intended to be limited to the detailsshown, since various modifications and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. In a method of smeltingiron-containing materials wherein said materials descend as a column ina shaft furnace above the floor thereof and are heated adjacent saidfloor so as to form thereon a liquefied-iron melt on which floats alayer of slag and to form on the inside wall of said furnace aniron-scale deposit, the improvement comprising the step of withdrawingliquefied iron from said melt and slag from said layer in such mannerthat said layer of slag always remains at the level of said deposit andsaid wall is thereby protected from said slag by said deposit.
 2. Amethod of smelting comprising the steps of:feeding iron-containingmaterials into the top of a shaft furnace to form therein an uprightcolumn of said materials; forming a flame above the floor of saidfurnace; heating the base of said column with said flame to melt thematerials at the base of said column into a liquefied-iron melt on saidfloor and a layer of slag on the surface of said melt and to form insaid furnace adjacent said base and on the wall of said furnace adeposit; supporting said column on said deposit; withdrawing said slagfrom said furnace at a location substantially level with said depositand above said surface in such a manner that said slag in said furnaceremains generally level with said deposit; withdrawing said melt fromsaid furnace at a location below said surface of said melt continuouslyin such a manner that said surface remains generally level with saiddeposit, whereby the wall of said furnace is protected from said slag bysaid deposit; and heating the withdrawn melt continuously during thewithdrawal thereof to maintain same molten.
 3. The method defined inclaim 2 wherein as said melt is withdrawn from said furnace said melt isconducted along a path having an upstream end at said location belowsaid surface and a downstream end substantially level with said surface,said path lying entirely below its said ends.
 4. The method defined inclaim 2 wherein said flame is formed by mixing and burning oxygen and acombustible in said furnace in a region level with said deposit, wherebysaid walls of said furnace is protected from said flame by said deposit.5. The method defined in claim 2 wherein said deposit has an upper edgeand a lower edge and said slag has an upper surface and a lower surface,said slag and said melt being withdrawn in such a manner that said uppersurface of said slag lies always below said upper edge of said depositand said lower surface of said slag lies above said lower edge of saiddeposit.